This application is based upon and claims priority to German Patent Application 199 44 748.9 filed Sep. 17, 1999, which application is herein expressly incorporated by reference.
The invention relates to a side strut for a lower steering arm of a tractor. Side struts are used to at least temporarily stabilize lateral pivotable lower steering arms of a tractor. Side struts prevent the lower steering arms from being pivoted. The side struts are designed such that, when an implement is lifted, the implement and the lower steering arms are automatically centered centrally relative to the longitudinal axis of the tractor. Furthermore, the side struts serve to hold the lower steering arms at a predetermined distance from one another in accordance with the category of the to be attached implement. This enables the implement to be coupled automatically from the driver""s seat.
DE 197 37 318 A1 discloses an assembly where one lower steering arm of a tractor attaching device is associated with a single-action, double-stage telescopic cylinder. The other lower steering arm is associated with a single-action, single-state hydraulic cylinder in the form of a side strut. The piston rod of the single-stage hydraulic cylinder includes a bore with a freely movable guiding rod. At its free end, the guiding rod or the piston rod of one of the two cylinders includes a thread to receive an attaching element to connect to the lower steering arm. The attaching element can be threaded over a shorter or longer distance. One stage of the double-stage telescopic cylinder serves to compensate for any play and to adapt to a certain category. A tension spring is arranged between the attaching means associated with the piston rod and the outside of the cylinder housing. The tension spring loads the pistons and the guiding rod to enable them to assume their moved-in positions. The tension spring is arranged eccentrically relative to the longitudinal axis of the side strut. In consequence, the spring is unprotected, so that the dimension of spread between the two lower steering arms changes if no implement is attached. In order to couple the implement, the correct dimension of spread has to be re-set. Furthermore, the effect of the spring may be adversely affected by rough operating conditions.
DE-GM 19 749 38 describes side struts that are associated with the lower steering arms of a tractor. Each side strut has a tube with a first attaching means and an adjustable journal. The adjustment is limited by stops. A further attaching means is also provided. If the lower steering arms are connected to one another by a liftlink drawbar, the connection with the lower steering arms can be effected to ensure free lateral movability or that such movability is eliminated. In addition, any play can be compensated for by the play of the thread. A central setting effect from a certain lifted position of the lower steering arm onwards is not possible.
DE 197 44 328 C1 describes a side strut which can be used for the lower steering arms of a tractor. The side strut has a single-action hydraulic cylinder with a piston and a cylinder housing. One end of a piston rod associated with the piston projects from the cylinder housing. The rod carries a first attaching means which is connected to a corresponding attaching means at the rear of the tractor.
The cylinder housing is axially followed by a hollow cylinder. An adjustable rod-shaped setting element is arranged in the hollow cylinder. The setting element is guided in the hollow cylinder by two spaced guiding rings. A pressure spring is arranged between the guiding rings. The spring is loaded into a moved-in position in which the setting element, by means of one end face, is supported against the base of the cylinder housing. The piston and the setting element can be moved out in opposite directions. The end of the setting element projects from the hollow cylinder when the setting element is moved in. The setting element includes a threaded bore which is engaged by a threaded rod. The second attaching means is attached to the threaded rod and is connectable to the associated lower steering arm. The basic axial length resulting from arranging the cylinder housing, the hollow cylinder, and the setting device for the category setting means with the threaded bore and the threaded bar one behind the other is too great for the installation conditions prevailing in modern tractors. Thus, the pivoting path of the lower steering arm is restricted.
It is an object of the invention to provide a side strut which is as short as possible. Also, a side strut is provided where the position of the piston in the cylinder housing remains unaffected by the spring.
In accordance with the invention, a side strut includes a single-action hydraulic cylinder. The single-action hydraulic cylinder has a cylinder housing, a piston including a hollow cylinder and a base closing one end of the hollow cylinder. The end of the piston with the base enters the cylinder housing. The hollow cylinder is guided out of the cylinder housing. The piston in the cylinder housing is movable along a longitudinal axis. The single-action hydraulic cylinder, further includes a first attaching means. The side strut further includes a setting means. The setting means includes a rod-shaped setting element arranged in the hollow cylinder. The rod-shaped element is co-axially arranged in the hollow cylinder and rotatable around the longitudinal axis. The rod-shaped element is also adjustable relative to the hollow cylinder between a first position, where it is moved into the hollow cylinder, and a second position, where it is moved out of the hollow cylinder. The setting element has a threaded bore arranged and centered on the longitudinal axis. The threaded bore starts from a second end face which projects from the open end of the hollow cylinder. The setting means further includes a spring means arranged in the hollow cylinder around the setting element. The spring means is effective between the piston and the setting element only. The spring means loads the setting element to enable the setting element to assume the moved-in position. The setting element, via a first end face, is in contact with the base face of the base of the piston in the moved-in position. The spring means allow the setting element to be adjusted in a direction which corresponds to the direction in which the piston is moved out of the cylinder housing. The setting means further include an actuating means to enable rotational displacement of the setting element. The setting means further includes a threaded rod connected to the second attaching means. The threaded rod is displacably received in the threaded bore of the setting element.
The telescopic design achieves short lengths between the attaching means. As a result, when use is made of the lower steering arms of a tractor, the lower steering arms include a great lateral freedom of movement. In addition, because the piston and the setting element move in the same direction when they are moved out, a short buckling length is achieved. This is advantageous from a buckling strength viewpoint. It is also advantageous that the spring means is protected. Thus, when the setting element is in the moved-in condition, the spring means hold the setting element by a first end face in contact with the base face of the base of the piston. The thread enables an adjustment to a certain category and to eliminate play when the implement is coupled. The spring only serves to adjust the setting element. It has no influence on the position of the piston in the cylinder.
According to a preferred embodiment, a setting element is guided through two guiding rings in the hollow cylinder. A first guiding ring and a second guiding ring are arranged on the outer face of the setting element. The compact arrangement is further improved by securing the first guiding ring in the hollow cylinder at the end removed from the cylinder housing in the moving-out direction of the setting element. The second guiding ring is secured at the end of the setting element, which faces the base of the piston, in a direction corresponding to the moving-in direction of the setting element. The spring means is arranged between the two guiding rings and between the outer face of the setting element and the inner face of the hollow cylinder. The spring means is in the form of a pressure element. The setting element is rotatably held in the two guiding rings.
By rotating the setting element, the length between the attaching means is changed. To facilitate such rotation, the actuating means are provided by an actuating lever attached to the setting element end which projects from the hollow cylinder. The actuating lever can be secured to the holding means in order to prevent any unintentional adjustment.
The first attaching means is preferably connected to the cylinder housing. A particularly compact design is achieved by arranging the threaded bore in the setting element such that, in the moved-in condition of the setting element, the setting element is at least partially positioned inside the hollow cylinder and thus inside the piston. Extremely short lengths are achieved so that a particularly advantageous short buckling length is also achieved.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.